A082704 Numbers k such that (28*10^(k-1) + 17)/9 is a depression prime.

3, 13, 15, 31, 105, 127, 343, 601, 9825

Offset: 1

Author

Patrick De Geest, Apr 13 2003

Keywords

• nonn
• base
• more

Comments

Prime versus probable prime status and proofs are given in the author's table.

a(10) > 2^16. - Lucas A. Brown, Apr 18 2021

a(10) > 2*10^5. - Tyler Busby, Feb 01 2023

Examples

			k=15 -> (28*10^(15-1) + 17)/9 = 311111111111113.
		

References

• C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.

Links

• Patrick De Geest, PDP Reference Table - 313.
• Makoto Kamada, Prime numbers of the form 311...113.
• Index entries for primes involving repunits.

Crossrefs

Cf. A082697-A082720, A056251, A068650.

Formula

a(n) = A056251(n) + 2.

Extensions

Edited by Ray Chandler, Nov 04 2014